Polyvinyl chloride resin composition having excellent transparency, surface gloss and impact strength

ABSTRACT

PVC resin compositions of improved transparency, surface gloss and impact resistance are obtained by mixing the PVC with a graft polymer. The graft is produced by grafting first methyl methacrylate and then styrene onto an elastomer of butadiene, nbutyl acrylate, and styrene in the proportions shown in the accompanying ternary constitutional diagram. When the monomer(s) used in preparing the aforesaid graft polymer have a small quantity of C10 to C18 saturated fatty acid dissolved therein, the PVC compositions prepared from the graft polymer show further improvements in their properties.

United States Patent [45] Feb. 22, 1972 Ide et al.

[54] POLYVINYL CHLORIDE RESIN [56] References Cited COMPOSITION HAVINGEXCELLENT UNITED STATES PATENTS TRAN PAREN R AND lillpAcT GLOSS3,288,886 11/1966 Himei et al. ..260/876 3,312,756 4/1967 Baer et al..260/876 [72] Inventors: Fumio Ide; Kenji Okano; Seiji Deguchi, all

of Hiroshima, Japan Primary ExaminerDonald F. Czaja AssistantExaminerDonald J. Barrack [73] Assgnees" 22:;25"; if; m"Attorney-William D. Hall, Elliott I. Pollock, Fred c. Philpitt, y pGeorge Vande Sande, Charles F. Steininger and Robert R. [22] Filed: July8, 1969 Priddy [21] Appl. No.: 839,946 ABSTRACT [30] Foreign ApplicationPriority Data PVC resin compositions of improved transparency, surfacegloss and impact resistance are obtained by mixing the PVC July 10, 1968Japan ..43/48360 ith a raft olymer, The graft is produced by graftingfirst July I2, Japan methyl methacrylate and then tyrene onto anelastomer of butadiene, n-butyl acrylate, and styrene in the proportions[52] US. Cl ..260/23.7 R, 260/23 XA, 260/23.7 M, Shown in theaccompanying ternary constitutional diagram Int Cl When the monomer(s)used in preparing the aforesaid graft polymer have asmauquantity ofcmtoC18 Saturated fatty acid [58] Field of Search ..260/876, 23.7,23 X, 890,80.7 dissolved therein the PVC Compositions prepared from the graftpolymer show further improvements in their properties.

4 Claims, 1 Drawing Figure POLYVINYL CHLORIDE RESIN COMPOSITION HAVINGEXCELLENT TRANSPARENCY, SURFACE GLOSS AND IMPACT STRENGTH The presentinvention relates to a resin composition mainly comprising a polyvinylchloride resin (hereinafter called PVC resin) and having excellenttransparency, high impact strength, and good surface gloss, inparticular, to a resin composition comprising 97-60 parts by weight of aPVC resin and 3-40 parts by weight of a graft polymer prepared bypolymerizing first methyl methacrylate in the presence of an elastomerobtained by copolymerizing 75-30 percent by weight 1,3-butadiene, 5-30percent by weight n-butyl acrylate, and -50 percent by weight styreneand thereafter polymerizing styrene.

Furthermore, when in the case of polymerizing the monomers in thepresence of the elastomer, a higher saturated fatty acid is added to atleast one of the monomers, the graft polymer obtained greatly enhancesthe processability and the impact strength of the PVC resin composition.

PVC resins are generally inexpensive and have excellent chemical andphysical properties. Thus, they are produced commercially on a largescale for many widely varying uses. However, such resins are somewhatinferior in impact strength and hence various studies have been made forovercoming such a difficulty and various improvements have beenreported.

It has been suggested that the impact resistance of PVC resins could beimproved by blending them with natural or synthetic rubber, or athermoplastic resin having such rubber as the base. Although thusobtained modified PVC resin composition shows an improved impactstrength as compared with that of the original PVC resin, thecomposition is generally inferior severely in transparency, that is, thetransparency which is one of the merits of PVC resin is severely reducedby improving the impact strength.

It has also been reported that when PVC resin is blended with a resinprepared by graft polymerizing a monomer such as styrene, methylmethacrylate, acrylonitrile, etc., to an elastomer such as polybutadieneor styrene-butadiene copolymer (hereinafter called SBR), a compositionhaving an improved impact resistance could be obtained without fatallyreducing the transparency of PVC resin. However, even in such case, theresin composition prepared has such demerits that the transparencythereof is insufficient and the surface properties of the final productsuch as the surface gloss and smoothness are degraded by the particlesize control of the elastomer, which is an important factor required formaintaining the transparency at the preparation of the composition.

In other words, in the case of using polybutadiene or SBR as theelastomer, the composition having excellent transparency cannot beobtained without reducing the particle size of the elastomer as small aspossible but the composition obtained by blending a PVC resin with agraft polymer prepared by usingthe elastomer having small porticle sizehas such faults that the surface gloss of PVC resin is reduced and themelt viscosity is i high.

An object of the present invention is to improve a low impact strengthof PVC resin without reducing the transparency and the surface glossthereof.

Other object of this invention is to provide a resin composition havingexcellent transparency, high impact resistance and good surface glosseven if a PVC resin having a relatively low polymerization degree.

Further object of this invention is to provide a resin compositionhaving excellent transparency, high impact resistance, and good surfacegloss even by using a molding machine having a weaker mixing power.

As the results of various investigations for obtaining the compositionwithout having aforesaid faults, the inventors have found an elastomerdifferent from conventional elastomers provides a resin compositionhaving excellent properties and by using such elastomer and selectingthe combination of the monomer to be graft polymerized to the elastomerand the polymerization conditions, an excellent resin composition havingimproved impact strength together with excellent transparency and goodsurface gloss can be ob-' tained.

The portion-within area ABCD in the ternary constitutional diagram ofthe accompanying drawing shows the range of the initial monomercomposition constituting the elastomer of 1,3-bitadiene, n-butylacrylate, and styrene used for preparing the resin composition of thepresent invention. Straight line I in the figure stands for theazeotropic composition in which the initial monomer composition ofl,3-butadiene, n-butyl acrylate, and styrene is same as the compositionthereof in the polymer formed at any moment of polymerization and theazeotropic composition gives the most excellent transparency to theterpolymer itself. Straight line m stands for the composition providingan index of refraction like that of polyvinyl chloride.

By only using the elastomers having such compositions as above, the hightransparency can be provided to copolymers prepared therefrom. Howeverif one of such a monomer as other acrylic ester than n-butyl acrylate,vinyl chloride, vinylidene chloride, or acrylonitrile instead of n-butylacrylate in the elastomer are used, the elastomer thus prepared cannotgive a resin composition having excellent transparency, high impactresistance, and good surface gloss.

The merit of using the aforesaid elastomer in the present invention isthat the control of the particle size of the elastomer is not soimportant as in the case of using polybutadiene of SBR. For example, inthe case of using polybutadiene or SBR, a good transparency cannot beprovided to a PVC resin composition if the elastomer particles havingparticle sizes less than 0.2 micron are not present therein in aproportion of higher than percent. On the other hand, in the case ofusing the aforesaid elastomer of this invention, a good transparency canbe provided to a resin composition even if the elastomer particleshaving the particle sizes of higher than 0.2 micron are present in aproportion of only about 40 percent by weight. Thefact that such a largeparticle size elastomer can be used for providing the PVC resincomposition having a good transparency greatly contributes to improvethe surface gloss of the PVC resin composition and maintain stableproperties of the compositions when molded or worked under variousconditions.

Moreover, when SBR is employed as the elastomer, the resin has unevenstructure and also the transparency and other properties of the finalproduct are largely influenced by the conversion of polymerization ofSBR since the structure and the refractive index thereof are varied bythe variation in conversion of polymerization thereof. On the otherhand, as the elastomer used in the present invention has an azeotropiccomposition or a composition similar to the azeotropic composition, theelastomer is scarcely influenced by the conversion of polymerization andhas a very homogeneous structure.

The composition of the present invention comprises graft polymer (I)prepared by grafting methyl methacrylate and then styrene to a1,3-butadiene-n-butyl acrylate-styrene elastomer (hereinafter, calledelastomer (E)") and PVC resin (II).

Graft polymer (l) which is one component of the resin composition ofthis invention may be prepared by grafting first methyl methacrylate toelastomer (E) while adding the monomer to a latex of the elastomer inone fell swoop or continuously and then grafting styrene thereto whileadding the styrene in one fell swoop or continuously (process A) but inorder to particularly facilitate the kneading of the graft polymer withPVC resin, the graft polymerization is conducted by dissolving asaturated fatty acid having 10-18 carbon atoms in at least one of methylmethacrylate and styrene to be graft polymerized in an amount of 0.5-5parts by weight per parts by weight of the graft polymer and addingcontinuously the solution to the polymerization system (process B).

The resin composition comprising the graft polymer prepared by any ofthe aforesaid processes and a PVC resin has an excellent surface glossand also even when a PVC resin having a low average degree ofpolymerization is employed, a resin composition having a very highimpact strength can be obtained. On the other hand, when a graft polymerprepared by grafting a mixture of methyl methacrylate and styrenesimultaneously to the elastomer is employed, the resin compositionobtained is inferior in surface gloss and also if the average degree ofpolymerization of the PVC resin employed is lower, the composition isalso inferior in impact strength.

Furthermore, when the graft polymer prepared by using the monomers, atleast one of which contains a saturated fatty acid having l-l 8 carbonatoms is employed, the resin composition prepared is very effective forproviding a product having excellent surface gloss and high impactstrength by using a molding machine having a weak kneading power.

The typical examples of the saturated fatty acids used in process Bshown above there are capric acid, palmitic acid, lauric acid, myristicacid, and stearic acid and they may be used alone or as a mixturethereof.

In the case of conducting the graft polymerization by process A, methylmethacrylate and/or styrene may be added in one fell swoop or may beadded continuously.

When the monomer is added continuously, the sheet or film formed byextruding the resin composition is superior in surface gloss and theboard of the composition formed by molding is superior in transparenceas compared with the case of adding the monomer in one fell swoop butthe impact strength of the resin composition is low in the former case.

On the other hand, in process B wherein the saturated fatty acid isemployed, it is necessary to add continuously the monomer containing thesaturated fatty acid to elastomer (E) over an at least 30-minute periodand otherwise, a large amount of coagulates are formed, which reduce thetransparency and the surface gloss of the final product.

Furthermore, it is necessary that graft polymer (I) be composed of 3070percent by weight elastomer (E) and 70-30 percent by weight the totalamount of methyl methacrylate and styrene to be grafted thereto, andalso the graft monomer to be grafted be composed of 10-50 percent byweight of methyl methacrylate and 90-50 percent by weight of styrene. Ifa graft polymer having other composition than above is employed, atleast one of the transparency, impact resistance, surface gloss andother mechanical properties of the resin composition prepared therefrombecomes low.

The graft polymerization is generally carried out at a temperature of30-l 00 C. in the presence ofa usual polymerization initiator.Furthermore, if necessary, a small amount of an emulsifier, a chaintransfer agent and a modifier may be employed.

The latex of the graft polymer thus prepared is coagulated by a knownmethod, washed with water and then dried.

PVC resin (H) which is other component of the resin composition of thepresent invention may be polyvinyl chloride or a copolymer of more than70 percent by weight of vinyl chloride and less than 30 percent byweight of at least one monomer of vinyl bromide, vinylidene chloride,vinyl acetate, acrylic acid and methacrylic acid. The PVC resin used inthe present invention may be prepared by a conventional emulsionpolymerization, suspension polymerization, or bulk polymerization.

For obtaining the resin composition of this invention, 3-40 parts byweight of graft polymer (1) is blended with 97-60 parts by weight of PVCresin (II) to provide 100 parts by weight of the final product. When theproportion of graft polymer (1) is less than 3 parts by weight, noeffect of adding the polymer is obtained, while if the proportion of thepolymer is higher than 40 parts by weight, other excellent properties ofPVC resin than transparency will be lowered as well as the use of such alarge proportion of polymer is not economical. The particularlypreferable composition of the present invention comprises lO-30 parts byweight of graft polymer (I) and 90-70 parts by weight of PVC resin (ll).

Graft polymer (1) is blended with PVC resin (H) by using a conventionalmixing means. For example, they may be mixed by a mixing roll, a Banburymixer, or a plastograph as well as a molding machine such as acompounding extruder and a blow molder. Also, they may be premixed bymeans of a ribbon blender or a Henschel mixer before mixing them bymeans of the aforesaid mixing machine. Moreover, as mixing, there may beadded to the system, if necessary, a conventional stabilizer, aplasticizer, a lubricating agent, a pigment, a filler, etc.

Now, the invention will be explained more in detail by the followingexamples although the invention shall not be limited to them. In theexamples, part and percent" mean part by weight" and percent by weight"respectively.

EXAMPLE 1 Synthesis of Elastomer (E-l 1,3-Butadiene 57 parts n-Butylaerylate 10 parts Styrene 33 parts Potassium oleate 2 parts Potassiumpersulfate 0.3 parts t-Dodecylmerca tan 0.5 parts Deionized water 180parts The above mixture was charged in an autoclave and after purgingwith nitrogen, polymerization was carried out for 15 hours at 55 C. withstirring to provide the elastomer (E-l) with a conversion of 97 percent.

Preparation ol'Graft Polymer (G-l) Elastomer (E-l 50 parts Methylmethacrylate 20 parts Styrene 30 parts Potassium ersulfate 0.5 partsDeionized Water 200 parts Thus, according to the aforesaid composition,20 parts of methyl methacrylate and 0.2 part of potassium persulfatewere first added to a latex of elastomer (El and the mixture was reactedfor 3 hours at 70 C. Thereafter, 30 parts of styrene and remaining 0.3part of potassium persulfate were added to the product thus prepared andthen the graft polymerization was carried out for 3 hours at 70 C. toprovide a latex of graft polymer (6-1). The latex of graft polymer thusformed was coagulated by a 0.2 percent aqueous sulfuric acid solutionfollowed by washing with water and then drying to provide white powdersof graft polymer (G-l In a Henschel mixer were blended 10 parts byweight of the graft polymer and parts by weight of PVC resin (havingaverage degree of polymerization (P) of 750) together with 2 parts ofdibutyl-tin-maleate, 1 part of butyl stearate and 1 part ofdibutyl-tin-laurate per 100 parts of PVC resin for 20 minutes. Thecompound thus obtained was extruded by means of an extruder having T-dieto provide a sheet of the resin composition and the properties of thesheet were measured, the results of which are shown below.

Impact strength 71.6 kg.-cm./mm. Gloss" 96.0%

Luminous transmittance 80.6%

Haze 4.3%

(Note) Sheet impact strength measured according to B5. 15244955 (0.3-mm.sheet thick) Gloss= (Reflection index/Reflection index of PVC) X 100(percent) The reflection index (an angle of incidence of 60") wasmeasured by using a gloss meter UGV-Z (made by Toyo Rika InstrumentsInc., Japan) "Total luminous transmittance measured according to ASTMD-l003-6l ress molded sheet) Measured according to ASTM DlOUIl-olEXAMPLES 2-7 The elastomers having the compositions shown in Table lwere prepared and graft polymers were prepared using the elastomers. Thesame procedure as in Example 1 was conducted using the graft polymersand PVC (P 750) to provide the resin compositions of the presentinvention and the properties of them were measured. For comparison,other resin compositions than those of the present invention having thecomposition outside the area ABCD of the ternary constitutional diagramwere prepared and the properties of them were also measured.

Each graft polymer was prepared by grafting first 18 parts of methylmethacrylate in the presence of a latex containing 50 parts of elastomer(average particle size of 0.16 micron) and then by grafting 32 parts ofstyrene.

As clear from Table 2, the transparency of the resin compositionprepared by using polybutadiene or SBR as elastomer was largelyinfluenced by the particle size of the elastomer. That is, in the caseof using polybutadiene, the transparency of the resin composition wasreduced when the particle size of TABLE 1 Elastomer Total compositionluminous (percent) Position transmitin the PVC/graft Impact strengttance Example No. Bd BA St diagram polymer (kg.-em./mm.) (percentExample 2 57 10 33 a 92/8 58. 4 80. 6 Example 3. 57 10 33 a 85/15 87. 680. 2 Example 4- 45 12 43 b 02/8 55. 2 78. 6 Example 5. 45 12 43 1)85/15 81.4 77. 9 Example 6. 40 40 0 92/8 54. 0 78. 2 Example 7 40 20 400 85/15 79.1 77.1 Comparative Example 75 0 d 92/8 59. 6 75.0 ComparativeExample 2. 75 0 25 d 85/15 89.0 69.0 Comparative Example 3. 100 0 0 e92/8 61.2 69. 5 Comparative Example 4. 100 0 0 e 85/16 90.8 58.0Comparative Example 5 52 28 20 f 92/8 49. 6 62. 5 Comparative Example 6.52 28 20 1 85/15 I 70. 2 59.1 Comparative Example 7. 17 33 50 g 92/8 31.6 69. 4 Comparative Example 8. 17 33 50 3 85/15 40. 2 59. 8

(note):

Bd: 1,3-butadiene BA: n-butyl acrylate St: styrene As is clear fromTable 1, the use of elastomers having compositions defined by pointsincluded in the area ABCD in figure results in resin compositions havingexcellent transparency as compared to those prepared with the elastomerhaving compositions outside the area ABCD.

EXAMPLES 8-11 Elastomer/latices each having different average particlesize were prepared by using a mixture of57 percent 1,3-butadiene, 10percent n-butyl acrylate, and 33 percent styrene. Thereafter, 25 partsof methyl methacrylate was first grafted to 45 parts of the elastomersand then parts of styrene was grafted thereto to provide graft polymers.Resin compositions consisting of 20 parts of the graft polymers and 80parts of PVC (P750) were prepared and their luminous transmittances weremeasured, the results of which are shown in Table 2.

For comparison, comparative resin compositions prepared by using thesame amount of polybutadiene or SBR (23.5 percent styrene) were preparedand their luminous transmittances were also measured.

the elastomer was larger than 0.12 micron and also in the case of usingSBR as the elastomer, the transparency was reduced when the particlesize was larger than 0.18 micron. On the other hand, in the case ofusing the elastomer in the present invention, the resin compositionhaving good transparency was obtained even when the elastomer having acomparatively large particle size was employed.

This is because the elastomer used in the present invention has auniform component distribution, a good compatibility with and a nearlysame refractive index as those of PVC, and also provide a graft polymerhaving a high grafting efficiency since the elastomer is properlyswollen with the monomer to be grafted to the elastomer.

EXAMPLES 12-14 To parts of the elastomer consisting of 57 percent 1,3-butadiene, 10 percent n-butyl acrylate, and 33 percent styrene wasgrafted 50 parts of the monomers as shown in Table 3 to provide graftpolymers. The properties of the resin compositions consisting of 8 partsof the graft polymers and 92 parts of PVC having a degree ofpolymerization of 710 are shown in Table 3.

TABLE 2 6O TABLE 3 Total Average grain luminous Grafting MonomerGrafting Properties of the Elastomer size of the transmittance 5Composition products Example No. employed elastomer 1.) St MMA GlossHaze (7%) Example 8 Bd/BA/St- Example 12 90 10 I 82.6 134 57/10/33 0.0778.6 Example 13 70 30 1 94.5 4.9 Example 9 0.12 77.2 Example 14 60 40 196.5 4.0 Example 10 0.18 76.0 Comparative Example ll 0.23 73.9 Example17 70 30 ll 71.5 8.3 Comparative Comparative Example 9 Polyhuladiene0.07 69.4 Example 18 60 40 11 70.4 8.8 Comparative Comparative Example10 0.12 632 Example 19 9S 5 I 62.5 18.6

EXAMPLES 15 -18 To 55 parts of the elastomer consisting of 57 percent1,3- butadiene, 10 percent n-butyl acrylate, and 33 percent styrene wasgrafted methyl methacrylate while supplying continuously the methylmethacrylate having dissolved therein a saturated fatty acid over a1-hour period and then styrene was grafted to the product whilesupplying continuously the styrene having dissolved therein a saturatedfatty acid over a 1-hour period to provide a graft polymer. A resincomposition consisting of 10 parts of the graft polymer thus preparedand 90 parts of PVC (F 750) was extruded into sheet by means of anextruder equipped with a T-die and the properties of it were measured,

was added and grafted continuously by using a potassium persulfateinitiator at 70 C. first 12 parts of methyl methacrylate over a 2-hourperiod and the graft polymerization was continued for 1 hour withstirring. Thereafter, 28 parts of styrene was continuously added to thesystem and grafted over a 2- hour period and the graft polymerizationwas continued for 1 hour with stirring to provide a graft polymer. From10 parts of the graft polymer thus obtained and 90 parts of PVC (F 750)was prepared the resin composition. The impact strength, gloss andluminous transmittance of the composition were 78.2 kg.-cm./mm., 94.2percent, and 78.8 percent respective- What is claimed is:

1. A resin composition comprising 1. 3-40 parts by weight of a graftpolymer prepared by polymerizing first 10-50 percent by weight methylmethacrylate in the presence of 30-70 parts by weight of elastomer (E)prepared by copolymerizing a monomer mixture comprising 75-30 percent byweight 1,3-butadiene, 5-30 percent by weight n-butyl acrylate, and 20-50percent by weight styrene and having the component ratio within area(ABCD) in the ternary constitutional diagram of the accompanying drawingand then the results ofwhich are shown in Table w 25 polymerizing 90-50percent by weight styrene, the total TABLE 4 Monomer grafted (1st step)Monomer grafted (2d step) Impact Example Monomer strength Gloss No.(parts) Fatty acid (parts) Monomer Fatty acid (parts) (kg.-ern./mm.)(percent) 15 MMA() Stearic acid (1.0) St() Stearic acid (2.5).-.. 86, 493 16.. MMA(20) Myristic acid (1.0)... St(25) Myrlstic acid (2.0).-. 80.4 94 17 MMA(20) Palmitic acid (1.5). St(25) Palmitic acid (2.5). 82. 396 18.... MMAQQ) Stearic acid (1.0) St(3l) Stearic acid (1.0)-... 81. 994 EXAMPLE 19 To 55 parts of the elastomer consisting of 65 percent 1,3-butadiene. 12 percent n-butyl acrylate and 23 percent styrene was addedand grafted continuously by using a potassium persulfate initiator at 70C. first 17 parts of methyl methacrylate while supplying the monomerhaving dissolved therein 1 part of stearic acid over a 1-hour period.Thereafter, 28 parts of styrene having dissolved therein 2 parts ofstearic acid was added and grafted continuously at 70 C. over a 1-hourperiod to provide a graft polymer. From 7 parts of the graft polymer and93 parts of PVC (1 700), a resin composition was prepared. The impactstrength, surface gloss and luminous transmittance of the compositionwere 54.8 kg.-cm./mm., 95.2 percent and 80.6 percent respectively.

EXAMPLE 20 To 60 parts of the elastomer consisting of 57 percent 1,3-butadiene, 10 percent n-butyl acrylate, and 33 percent styrene amount ofsaid monomers being 70-30 parts by weight, and

ll. 97-60 parts by weight of polyvinyl chloride or 97-60 parts by weightof a copolymer comprising more than 70 percent by weight vinyl chlorideand less than 30 percent by weight at least one of vinyl bromide, vinylacetate, vinylidene chloride, acrylic acid and methacrylic acid.

2. The resin composition as claimed in claim 1 wherein said graftpolymer is prepared by polymerizing methyl methacrylate and styrenewhile adding continuously at least one of the monomers to the elastomerover an at least 30-minute period.

3. The resin composition as claimed in claim 1 wherein at least one ofmethyl methacrylate and styrene to be polymerized in the presence ofelastomer (E) has uniformly dissolved therein 0.5-5 percent by weightbased on said graft polymer of a saturated fatty acid having 10-18carbon atoms.

4. The resin composition as claimed in claim 1 wherein said elastomer(E) is a terpolymer comprising 55-60 percent by weight l,3-butadiene,8-13 percent by weight n-butyl acrylate, and 30-38 percent by weightstyrene.

2. The resin composition as claImed in claim 1 wherein said graft polymer is prepared by polymerizing methyl methacrylate and styrene while adding continuously at least one of the monomers to the elastomer over an at least 30-minute period.
 3. The resin composition as claimed in claim 1 wherein at least one of methyl methacrylate and styrene to be polymerized in the presence of elastomer (E) has uniformly dissolved therein 0.5-5 percent by weight based on said graft polymer of a saturated fatty acid having 10-18 carbon atoms.
 4. The resin composition as claimed in claim 1 wherein said elastomer (E) is a terpolymer comprising 55-60 percent by weight 1,3-butadiene, 8-13 percent by weight n-butyl acrylate, and 30-38 percent by weight styrene. 